The present invention relates to a method for obtaining protein-containing animal feed from organic substances dissolved and/or suspended in water, where the substances are biologically processed in at least two series-connected steps which have an activating tank and a settling tank.
From DE-OS No. 26 14 875, a two-stage activated-sludge process is known by which waste water is purified. This activated sludge method is not suited for the purification of liquid manure from agriculture operations since liquid manure is loaded with too high a percentage of organic matter. Furthermore, this method has up to now been used only for the purification of waste water.
It is further known from German Pat. No. 22 42 377 to dehydrate excess sludge produced in the biological breaking-down of waste water and to heat it in a thin layer for a short time in order to decompose the bacteria cells.